When to use private hosted zones and public hosted zones

Can you explain the main difference between private hosted zones and public hosted zones in Amazon Route 53?

The main difference between private hosted zones and public hosted zones in Amazon Route 53 is scope and access. A public hosted zone is accessible over the internet by the general public, whereas a private hosted zone is restricted and only accessible within one or more specified Amazon Virtual Private Clouds (VPCs). Public hosted zones typically host DNS records for domain names intended to be publicly resolvable. In contrast, private hosted zones contain records relevant to resources within a VPC that do not need to be accessed from the open internet.

When would an organization opt to use a private hosted zone over a public hosted zone?

An organization would opt to use a private hosted zone when it needs to resolve domain names that are not intended to be public, often within an internal network, such as a company’s intranet, or resources within their AWS VPC that should not be accessible from the internet, like internal APIs, databases, or application servers.

How can DNS query resolution differ between private and public hosted zones, considering a scenario where both are configured for a domain in AWS?

If both private and public hosted zones are configured for the same domain, DNS queries from resources within the VPC will resolve to the records in the private hosted zone. In contrast, DNS queries from the public internet will resolve to the records in the public hosted zone. This allows for a split-view DNS setup where internal and external resolutions can be handled differently.

Is it possible to associate a private hosted zone with more than one VPC? If so, in what scenarios is this useful?

Yes, it is possible to associate a private hosted zone with more than one VPC. This feature allows you to centralize and share DNS for private domains across multiple VPCs, which is useful when you have resources that span multiple VPCs and need consistent internal name resolution, such as in multi-account strategies or with VPC peering arrangements.

In what situation would you migrate from using a public hosted zone to a private hosted zone?

You might migrate from using a public hosted zone to a private hosted zone when a service or application that was once publicly available is moved to an internal network and should no longer be accessible from the internet. Or, during the development stage, where public access is not yet appropriate.

When setting up a hybrid cloud architecture, how would you decide whether to use a private or public hosted zone for your services?

For a hybrid cloud architecture, a private hosted zone is used when the services need to be accessible within an AWS VPC and possibly on-premises environments connected via AWS Direct Connect or a VPN, and not accessible to the public internet. A public hosted zone would be used for services that need to be accessible from anywhere on the internet. The decision often depends on the intended audience and access needs.

Can you have overlapping namespaces between private and public hosted zones in AWS Route 53? What might be the implications?

Yes, you can have overlapping namespaces between private and public hosted zones in AWS Route 53, which essentially creates a split-horizon DNS scenario where the DNS response depends on the location of the requestor. However, this can lead to complications and requires careful DNS management to ensure it does not lead to resolution conflicts or access control issues.

If a company uses a private hosted zone, how could they ensure on-premises resources resolve to the correct internal IP addresses within the AWS environment?

To ensure on-premises resources resolve to the correct internal IP addresses within the AWS environment, the company can use a DNS forwarding mechanism from their on-premises DNS server to the AWS DNS servers associated with their VPC. This setup allows on-premises systems to resolve names in the private hosted zone.

What are some of the security benefits for an organization hosting their internal DNS records in a private hosted zone?

Hosting internal DNS records in a private hosted zone can improve security by ensuring that internal structure and resources are not revealed to the public internet, reducing the exposure to potential DNS-based attacks, and by providing an additional layer of access control to DNS information which is critical for secure operations.

Can you configure a private hosted zone to be accessible over the internet if required for certain use cases?

A private hosted zone itself is not accessible over the internet; it’s designed to be private and accessible only from within designated VPCs. If internet accessibility is required, services should be registered in a public hosted zone. However, for specific cases, such as a temporary need for external access, you can create a VPN connection or use AWS Direct Connect to simulate internal access, although this might not be practical for widespread public usage.

Describe a situation in which you would use both a private and a public hosted zone for the same domain name in AWS.

You would use both a private and a public hosted zone for the same domain name when you need to provide a split-view DNS. For example, suppose you have internal resources that should resolve to private IP addresses for users within your VPCs (using a private hosted zone) and a public website that should resolve to a public IP address for users on the internet (using a public hosted zone). This allows for internal and external DNS queries for the same domain name to be handled differently, based on the query’s source.

How does Route 53 handle health checks and DNS failover with private hosted zones compared to public hosted zones?

Health checks and DNS failover are features more typically used with public hosted zones rather than private hosted zones because they are designed to redirect traffic in case of endpoint failures, which is generally a concern for publicly accessible services. Private hosted zones typically address internal resources that may not require the same level of health monitoring and traffic management designed for internet-facing services. However, Route 53 does support health checks for private hosted zones if needed, but traffic redirection would typically be within the private network infrastructure.